We shall compare the relative amounts of Hb F1 in red cells isolated from individuals with disorders accompanied by elevated Hb levels, e.g. sickle cell anemia, homozygous beta-thalassemia, S-beta thalassemia, juvenile chronic myeloid leukemia, and hereditary persistence of fetal hemoglobin. The ratio of glycine to alanine at residue 136 of the gamma chain of Hb F1 from these cells will also be determined. The finding that Hb F1 is present in some disorders but not others and has a "fetal-like gamma136 glycine/alanine ratio of 3/1 would be consistent with a clonal origin for the acetylated hemoglobin.